In the continuing exploration of space, the National Aeronautics and Space Administration (NASA) is developing and implementing a comprehensive program of research and technology for monitoring the stratosphere to obtain increased knowledge and understanding of the physics and chemistry of the upper atmosphere. The development of highly sensitive instruments for remotely measuring the important chemical constituents of the atmosphere is an important aspect of this research. These instruments typically have a requirement for cryogenic cooling of the sensitive detectors and components that are necessary to detect the presence of the tenuous constituents of the atmosphere. Due to the extreme sensitivity of these instruments, it is necessary that the cryogenic coolers be closely integrated with the detectors to assure that temperature requirements will be satisfied and that the mechanical interfaces will be acceptable.
Future instruments will be required to perform a variety of missions including ground based observations, aircraft flights, balloon launches, rocket flights, and shuttle orbital missions. To satisfy the diverse requirements of these missions, increasing consideration is being given to closed cycle mechanical refrigerators to satisfy the need for efficient, reliable, and convenient cryogenic cooling.
However, the use of mechanical refrigerators can introduce dynamic vibration effects which have adverse effects on instrument performance. Since instrument detectors are optically coupled through the instrument to a signal source, any movement of the detector may result in defocusing and degradation of the instrument resolution. In addition, active elements such as tunable diode lasers (TDL) which may be used to generate a local oscillator reference signal in a heterodyne instrument are themselves sensitive to vibration and exposure to a dynamic environment may cause a shift in output frequency which will also have a deleterious effect on instrument sensitivity.